1. Field of the Invention
The present invention relates to an image reading apparatus and more particularly, to an image reading apparatus applied to a color scanner, a color facsimile or the like, which uses a unit CCD sensor to flash sequentially three fluorescent lamps of red, green and blue lights as light sources in accordance with the scanning period of the CCD sensor, and to detect by the CCD sensor the reflected lights from the image to perform the color resolution.
2. Description of the Prior Art
Conventionally, FIG. 1 through FIG. 3 show an optical system in an image reading apparatus which is the background of this invention, and to which one embodiment of the present invention is applied. In an example shown in FIG. 1, there are provided an R fluorescent lamp 2 which transmits a red light to a color manuscript 1, a G fluorescent lamp 3 which transmits a green light thereto, and a B fluorescent lamp 4 which transmits a blue light thereto. The reflected lights from the color manuscript 1 in accordance with the lights from the fluorescent lamps 2 through 4 are focused with a lens 6 from a mirror 5 and are input into the CCD sensor 7.
In an example shown in FIG. 2, only a fluorescent lamp 8 of ordinary light is provided for the color manuscript 1. The reflected light from the color manuscript 1 in accordance with the light from the fluorescent lamp 8 is reflected by the mirror 5 and is separated into the respective light components of the red, green, blue of the color manuscript 1 by a filter disk 9 so as to be input into the CCD sensor 7 through the lens 6.
In an example shown in FIG. 3, a dichroic mirror 10, instead of a filter disk 9 shown in FIG. 2, is disposed behind the lens 6 to separate the light of the color manuscript 1 into the light components of the red, green, blue thereof so as to be respectively input into an R reading CCD sensor 11, a G reading CCD sensor 12 and a B reading CCD sensor 13.
The CCD sensors 7, 11 through 13 shown in the above-described FIG. 1 through FIG. 3 output light electric-charge from the light incidence. The light electric-charge not shown is loaded on an analog shift register and is sequentially shifted in accordance with a clock pulse. The electric charge caused due to some light leakage is added later while the content loaded on the analog shift register is being shifted. Namely, the electric charge from the sensor portion to the analog shift register is not completely transferred by one shift, thus resulting in some short shipment of the remaining load. The above-described two facts are responsible for deterioration in the accuracy of the color resolution in the conventional image reading apparatus, and measures against them have not been taken at all or have been neglected.